40 th national science olympiad: 4 march 2004 questions … · 2019-01-08 · 1 40 th national...

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40th NATIONAL SCIENCE OLYMPIAD: 4 March 2004

QUESTIONS AND SOLUTIONS: BIOLOGY

1. Which order of the class Reptilia is

not found in Southern Africa?

1 Chelonia (Turtles and

marine turtles)

2 Crocodilia (Crocodiles)

3 Alligatoria (Alligators)

4 Rhynchocephalia (Tuatara)

5 Squamata (Lizards and

snakes)

Answer: 4 (Encyclopaedia Britannica)

The living reptiles belong to four orders: the

Squamata (lizards, snakes, and

amphisbaenians), the Rhynchocephalia (one

rare species, the tuatara of New Zealand),

the Chelonia (turtles), and the Crocodylia

(crocodiles and alligators).

The tuatara is a lizard-like animal and the

sole surviving member of the order

Rhynchocephalia,that may have appeared

as early as the Late Triassic Epoch (about

227 to 206 million years ago). Until recently

the tuatara lived on the two main islands of

New Zealand. Today it is found only on

certain islets in Cook Strait between the

main islands and on islets between East

Cape and North Cape of the North Island of

New Zealand. Tuataras are essentially

solitary, nocturnal, burrowing animals,

seldom travelling more than a few metres

from their burrows during the day. Feeding

takes place mainly at night. The principal

diet of the young is insects; adults eat—in

addition to insects—snails, lizards, young

seabird chicks, and eggs. They will drink

water if it is available but can survive for

months on water obtained from dew and

solid food. Male tuataras may attain a length

of 60 centimetres (about 24 inches) and a

weight of 1,000 grams (about 2.2 pounds).

Females grow to about 50 centimetres (20

inches) and sometimes weigh as much as

500 grams (1.1 pounds). Eight to 15 eggs

are laid in a nesting burrow covered by

several centimetres of soil. The young

emerge about 13 months later, in early

summer to midsummer. Adult size is not

reached for 50 to 60 years, and the animal

may live to the age of 100. Sexual maturity

is believed to occur after about 20 years.

2. Which animals are responsible for

the most deaths in humans?

1 Crocodiles

2 Snakes

3 Mosquitoes

4 Lions

5 Sharks


Mosquitoes are vectors for malaria; a

serious, relapsing infection in humans

characterized by periodic attacks of chills

and fever, anaemia, splenomegaly

(enlargement of the spleen), and often fatal

complications. It is caused by one-celled

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parasites of the genus Plasmodium that are

transmitted to humans by the bite of

Anopheles mosquitoes. Malaria can occur in

temperate regions, but it is most common in

the tropics and subtropics. In many parts of

sub-Saharan Africa, entire populations are

infected more or less constantly. Malaria is

also common in Central America, the

northern half of South America, and in South

and Southeast Asia. The disease also

occurs in countries bordering on the

Mediterranean, in the Middle East, and in

East Asia. In Europe, North America, and

the developed countries of East Asia,

malaria is still encountered in travellers

arriving or returning from affected tropical

zones. Annual cases of malaria worldwide

are estimated at 250 million, with more than

one million deaths resulting—most of them

young children in Africa.

3. Which fact about crocodiles is

incorrect?

1 In South Africa, they are

only found in rivers that flow

in an easterly direction

2 The main swimming organ

is the tail

3 They can stay under water

for up to one hour

4 the sex of the hatchlings is

determined by the average

temperature

5 Older crocodiles starve to

death because teeth are

only replaced twice


Crocodiles are generally large, ponderous,

amphibious animals, somewhat lizardlike in

appearance, and carnivorous in habit. They

have powerful jaws with many conical teeth

and short legs with clawed, webbed toes.

The tail is long and massive and the skin

thick and plated. About 20 species are

recognized. The crocodiles are the largest

and the heaviest of present-day reptiles. In

former times the Nile crocodile (Crocodilus

niloticus) and the estuarine crocodile

(Crocodilus porosus) attained a length of

almost nine metres (about 30 feet), but

today, specimens rarely exceed six metres

(20 feet). All crocodiles have a relatively

long snout, or muzzle, which varies

considerably in proportions and shape. The

large horny plates that cover most of the

body generally are arranged in a regular

pattern. Thick, bony plates occur on the

back. The families and genera may be

distinguished by anatomical features,

principally those of the skull. Crocodiles

continuously shed and replace their teeth.

4. Which animal has the longest

gestation period?

1 White rhinoceros

2 Atlantic right whale

3 African elephant

4 Giraffe

5 Bottlenose dolphin

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Gestation is the time between conception

and birth, during which the embryo or foetus

is developing in the uterus. This definition

raises occasional difficulties because in

some species (e.g., monkeys and man) the

exact time of conception may not be known.

In these cases the beginning of gestation is

usually dated from some well-defined point

in the reproductive cycle (e.g., the beginning

of the previous menstrual period). The

length of gestation varies from species to

species. The shortest known gestation is

that of the Virginian opossum, about 12

days, and the longest that of the elephant,

about 22 months. In the course of evolution

the duration of gestation has become

adapted to the needs of the species. The

degree of ultimate growth is a factor, smaller

animals usually having shorter periods of

gestation than larger ones. Marsupials

generally have short gestations—e.g., 40

days for the largest kangaroos. The young,

born in an extremely immature state,

transfer to the pouch in which gestation may

be said to continue.

White rhinos can live to be 50 years of age.

Gestation lasts approximately 16 months,

and mothers give birth to one calf every 2-3

years. Females reach sexual maturity

between 6 and 7 years of age; males mature

between 7 and 10 years of age.

The North Atlantic Right Whale (Eubalaena

glacialis) is a baleen whale, one of three

species formerly called classified as the

Right Whale belonging to the genus

Eubalaena. Adult right whales average 35-

55 feet (10.7-16.8 meters) in length and

weigh up to 70 tons (63,500 kilograms); the

largest measured have been 60 feet long

and 117 tons (106,500 kilograms). Females

are larger than males and first give birth at

age nine or 10 after a yearlong gestation.

Calves are 13-15 feet long at birth. There is

little data on their life span, but it's believed

to be at least 50 years, and closely related

species may live more than a century.

Giraffe females first breed at four or five

years of age. Gestation is 15 months, and,

though most calves are born in dry months

in some areas, births can take place in any

month of the year. The single offspring is

about 2 metres (6 feet) tall and weighs 100

kg (220 pounds). For a week the mother

licks and nuzzles her calf in isolation while

they learn each other's scent. Thereafter,

the calf joins a “nursery group” of similar-

aged youngsters, while mothers forage at

variable distances. If lions or hyenas attack,

a mother sometimes stands over her calf,

kicking at the predators with front and back

legs.

The average gestation period in bottlenose

dolphins is 12 months. The young are born

in shallow water, sometimes assisted by a

"midwife" (which may be male). A single calf

is born, about 1 m (3 ft) long at birth. To

speed up the nursing process, the mother

can eject milk from her mammary glands.

There are two slits, one on either side of the

genital slit, each housing one nipple. The

calf is nursed for 12 to 18 months. The

young live closely with their mother for up to

6 years; the males are not involved in the

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raising of their mother's subsequent

offspring.

5. What are “loggerheads and

leatherbacks”

1 Marine turtles

2 Ostriches

3 Whales

4 Ticks

5 Spiders

Answer 1: (Encyclopaedia Britannica)

The leatherback turtle (Dermochelys

coriacea) is the largest of living turtles and

may attain a total length of about 2.1 metres

(7 feet) with a weight of about 540 kilograms

(1,200 pounds) and a span of about 2.7 m

from the tip of one front flipper to the tip of

the other. Maximum reported lengths and

weights range up to 3 m and about 900 kg

but are poorly authenticated. The

leatherback has no visible shell. A shell is

present but consists of bones buried in the

dark brown or blackish skin. There are

seven pronounced longitudinal ridges on the

back of the turtle and five on the underside.

The leatherback is a strong swimmer and

inhabits open seas throughout the world. It

apparently is omnivorous and takes both

animal and plant material.

The loggerhead (Caretta caretta) is a large

turtle similar to the green turtle but with a

relatively larger head. It is reddish brown or

brown in colour. The loggerhead attains a

shell length of about 0.7–2.1 m. A large

specimen usually weighs about 135 kg, but

weights of almost 400 kg have been

recorded. The loggerhead, found in oceans

throughout the world, is a carnivorous reptile

with a reportedly bad disposition.

6. Robben Island is a world heritage

site but feral cats have had a huge

impact on the ground nesting bird

populations. What is the most

humane method used to control the

cat population?

1 Hunting

2 Poisoning

3 Euthanasia

4 Biological control by

infecting them with feline

parvovirus

5 Caught, sterilised and

released


Hunting would be too expensive, requiring

manpower. Euthanasia (merciful killing) or

Catching, sterilising and releasing the cats

would be even more expensive and labour

intensive. Poisoning will not be specific (no

poison can kill wild cats exclusively!). Thus,

the only option is biological control.

Parvovirus, commonly abbreviated to parvo,

is a genus of the Parvoviridae family linear,

non-segmented single stranded DNA

viruses with an average genome size of 5

kbp. Parvoviruses are some of the smallest

viruses found in nature (hence the name,

from Latin parvus meaning small). Many

types of mammalian species have a strain of

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parvovirus associated with them.

Parvoviruses tend to be specific about the

taxon of animal they will infect, but this is a

somewhat flexible characteristic. Thus, all

strains of canine parvovirus will affect dogs,

wolves, and foxes, but only some of them

will infect cats. No members of the genus

Parvovirus are currently known to infect

humans, but humans can be infected by

viruses from three other genera from the

Family Parvoviridae. Feline panleukopenia,

more commonly known as feline distemper,

is a viral infection affecting cats caused by

feline parvovirus. The virus primarily attacks

the lining of the gastrointestinal tract,

causing internal ulceration and, ultimately,

total sloughing of the intestinal epithelium.

This results in profuse, usually bloody

diarrhea, causing severe dehydration,

malnutrition, anemia, and often death;

mortality rate 60-90%.

7. The relationship between a

clownfish and anemones.

1 Mutualism

2 Parasitism

3 Commensalism

4 Altruism

5 Saprophytic


One of the best known cnidarian symbioses

is the mutualism between 10 species of

tropical anemones and 26 species of

anemone fish (such as the clown fish).

These fishes live within the protective field of

anemone tentacles, where they take refuge

when a predator threatens. Immunity of the

fishes to the stings of the nematocytes

results from the thin layer of mucus that

covers their bodies. It is unclear whether the

mucous is made by the fishes themselves,

or acquired by contact with the anemone's

tentacles. Without its mucus, the clown fish,

like any other small fish, may be stung to

death and eaten by the anemone. Anemone

fishes serve their hosts by driving away

fishes that prey on anemones. Other fishes

have a similar association with large

medusae.

8. What will probably occur if all

primary consumers are removed

from a closed ecosystem?

1 The producers will be

destroyed

2 Number of secondary

consumers will increase

3 Carnivores will start to die

4 Number of herbivores will

decrease

5 The carrying capacity of the

land will decrease


An ecosystem can be categorized into its

abiotic constituents, including minerals,

climate, soil, water, sunlight, and all other

nonliving elements, and its biotic

constituents, consisting of all its living

members. Linking these constituents

together are two major forces: the flow of

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energy through the ecosystem, and the

cycling of nutrients within the ecosystem.

The fundamental source of energy in almost

all ecosystems is radiant energy from the

sun. The energy of sunlight is used by the

ecosystem's autotrophic, or self-sustaining,

organisms. Consisting largely of green

vegetation, these organisms are capable of

photosynthesis—i.e., they can use the

energy of sunlight to convert carbon dioxide

and water into simple, energy-rich

carbohydrates. The autotrophs use the

energy stored within the simple

carbohydrates to produce the more complex

organic compounds, such as proteins, lipids,

and starches, that maintain the organisms'

life processes. The autotrophic segment of

the ecosystem is commonly referred to as

the producer level. Organic matter

generated by autotrophs directly or indirectly

sustains heterotrophic organisms.

Heterotrophs are the consumers of the

ecosystem; they cannot make their own

food. They use, rearrange, and ultimately

decompose the complex organic materials

built up by the autotrophs. All animals and

fungi are heterotrophs, as are most bacteria

and many other microorganisms. Together,

the autotrophs and heterotrophs form

various trophic (feeding) levels in the

ecosystem: the producer level, composed of

those organisms that make their own food;

the primary-consumer level, composed of

those organisms that feed on producers; the

secondary-consumer level, composed of

those organisms that feed on primary

consumers; and so on. The movement of

organic matter and energy from the

producer level through various consumer

levels makes up a food chain. For example,

a typical food chain in a grassland might be

grass (producer) → mouse (primary

consumer) → snake (secondary consumer)

→ hawk (tertiary consumer). Actually, in

many cases the food chains of the

ecosystem overlap and interconnect,

forming what ecologists call a food web. The

final link in all food chains is made up of

decomposers, those heterotrophs that break

down dead organisms and organic wastes.

9. Where do ticks and fleas spend

most of their time?

1 In tall grass waiting for a

host

2 In egg form

3 On the host

4 In the larval stage in sand

5 In the larval stage in water


A tick is any of about 825 species of

invertebrates in the order Parasitiformes

(subclass Acari). Ticks are important

parasites of large wild and domestic animals

and are also significant as carriers of serious

diseases. Although no species is primarily a

human parasite, some occasionally attack

humans. Hard ticks, such as the American

dog tick (Dermacentor variabilis), attach to

their hosts and feed continuously on blood

for several days during each life stage.

When an adult female has obtained a blood

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meal, she mates, drops from the host, and

finds a suitable site where she lays her eggs

in a mass and dies. Six-legged larvae hatch

from the eggs, move up on blades of grass,

and wait for a suitable host (usually a

mammal) to pass by. The odour of butyric

acid, emanated by all mammals, stimulates

the larvae to drop onto and attach to a host.

After filling themselves with the host's blood,

the larvae detach and moult, becoming

eight-legged nymphs. Nymphs also wait for,

and board, a suitable host in the same way

as larvae. After they have found a host and

engorged themselves, they also fall off, and

then they moult into adult males or females.

Adults may wait for a host for as long as

three years. Most hard ticks live in fields and

woods, but a few, such as the brown dog

tick (Rhipicephalus sanguineus), are

household pests. Soft ticks differ from hard

ticks by feeding intermittently, laying several

batches of eggs, passing through several

nymphal stages, and carrying on their

developmental cycles in the home or nest of

the host rather than in fields. Hard ticks

damage the host by drawing large amounts

of blood, by secreting neurotoxins (nerve

poisons) that sometimes produce paralysis

or death, and by transmitting diseases,

including Lyme disease, Texas cattle fever,

anaplasmosis, Rocky Mountain spotted

fever, Q fever, tularemia, hemorrhagic fever,

and a form of encephalitis. Soft ticks also

are carriers of diseases. Adults range in size

up to 30 mm (slightly more than 1 inch), but

most species are 15 mm or less. They may

be distinguished from their close relatives,

the mites, by the presence of a sensory pit

(Haller's organ) on the end segment of the

first of four pairs of legs. Eyes may be

present or absent. This group has a

worldwide distribution, and all species are

assigned to three families: Argasidae,

comprising the soft ticks, and Nuttalliellidae

and Ixodidae, together comprising the hard

ticks. The family Nuttalliellidae is

represented by one rare African species.

10. In order to continue to exist a

butterfly has to sit frequently. Which

one is not a reason for this

behaviour?

1 They have to take in water

frequently. Water is

relatively heavy and

influences the ability to fly

2 They have to take in

glucose frequently. Flying

uses a lot of energy

3 They cannot store water

and food in large quantities

4 Females have to lay eggs

over a large area

5 To pollinate flowers

Answer: 5

Butterflies do not consciously seek flowers

to pollinate them! Through eons, flowering

plants evolved traits that attracted insects to

land on their flowers (for feeding) and

inadvertently transfer them pollen grains as

they flew from flower to flower.

Lepidopterans (butterflies and moths) are

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attracted to flowers that are brightly coloured

and produce nectar. Typical moth flowers—

e.g., jimsonweed, stephanotis, and

honeysuckle—are light-coloured, often long

and narrow, without landing platforms. The

petals are sometimes fringed; the copious

nectar is often in a spur. They are open and

overwhelmingly fragrant at night. Butterfly

flowers—e.g., those of butterfly bush,

milkweed, and verbena—are conspicuously

coloured, often red, generally smaller than

moth flowers, but grouped together in erect,

flat-topped inflorescences that provide

landing space for the butterflies.

11. The stick insect makes use of ….

1 protective coloration

2 warning coloration

3 disruptive coloration

4 camouflage

5 mimicry


Walking stick, also called stick insect is any

of about 2,000 species of slow-moving

insects that are green or brown in colour and

bear a resemblance to twigs as a protective

device. Some species also have sharp

spines, an offensive odour, or the ability to

force their blood, which contains toxic,

distasteful chemicals, through special joints

in the exoskeleton. In many species the

eggs closely resemble seeds. Walkingsticks

are unusual among the insects in that they

have the ability to regenerate legs and

antennae. The front wings of some species

are short and leathery, whereas others have

large, colourful hind wings that are kept

folded over the abdomen. Walkingsticks

found in the tropics are the largest and most

abundant. Certain species, such as the

Asiatic Palophus and the East Indian

Pharnacia, are more than 30 cm (12 inches)

in length. The North American species

Diapheromera femorata may defoliate oak

trees during heavy infestations. Some

authorities place walkingsticks in the order

Phasmatodea, and some consider them as

a suborder (Phasmatodea) of the order

Orthoptera. Immobility usually makes

detection less likely. For stick insects and

other animals resembling twigs or leaves,

when immobility itself becomes conspicuous

against moving foliage, the animals'

compensatory swaying increases the

camouflage effect.

12. Which difference between

Monocotyledon and Dicotyledon

plants is correct?

Monocot Dicot

1 Net venated

leaves

Parallel venated

leaves

2 Petiole absent Petiole present

3 Compound leaves Simple leaves

4 Tap root system Adventitious root

system

5 Seeds have 2

lobes

Seeds have 1 lobe

Answer: 2 (Wikipedia)

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Aside from cotyledon number, other broad

differences have been noted between

monocots and dicots, although these have

proven to be differences primarily between

monocots and eudicots. Many early-

diverging dicot groups have "monocot"

characteristics such as scattered vascular

bundles, trimerous flowers, and non-

tricolpate pollen. In addition, some monocots

have "dicot" characteristics such as

reticulated leaf veins. Seeds: The embryo of

the monocot has one cotyledon while the

embryo of the dicot has two. Flowers: The

flower parts in monocots are multiples of

three while in dicots are multiples of four or

five. Stems: In monocots, the stem vascular

bundles are scattered, while in dicots they

are in a ring. Secondary growth: In

monocots, stems rarely show secondary

growth; in dicots, stems frequently have

secondary growth. Pollen: In monocots,

pollen has one furrow or pore while in dicots

they have three. Roots: The roots are

adventitious in monocots, while in dicots

they develop from the radicle. Leaves: In

monocots, the major leaf veins are parallel,

while in dicots they are reticulated.

13. Wind pollinated flowers usually have

1 large petals

2 strong aromas

3 large amounts of pollen all

and dry

4 stamens and stigmas re

situated inside the flower

5 brightly coloured petals


Wind-pollinated flowers are inconspicuous,

being devoid of insect attractants and

rewards, such as fragrance, showy petals,

and nectar. To facilitate exposure of the

flowers to the wind, blooming often takes

place before the leaves are out in spring, or

the flowers may be placed very high on the

plant. Inflorescences, flowers, or the

stamens themselves move easily in the

breeze, shaking out the pollen, or the pollen

containers (anthers) burst open in an

explosive fashion when the sun hits them,

scattering the pollen widely into the air. The

stigmas often are long and divided into arms

or lobes, so that a large area is available for

catching pollen grains. Moreover, in open

areas wind-pollinated plants of one species

often grow together in dense populations.

The chance of self-pollination, high by the

very nature of wind pollination, is minimized

by the fact that many species are dioecious

or (like hazel) have separate male and

female flowers on each plant. Familiar

flowering plants relying on wind pollination

are grasses, rushes, sedges, cattail, sorrel,

lamb's-quarters, hemp, nettle, plantain,

alder, hazel, birch, poplar, and oak. (Tropical

oaks, however, may be insect-pollinated.)

14. Which one has no DNA or RNA?

1 Red blood corpuscles

2 Viruses

3 Nucleus

4 Gamete

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5 Zygotes


Erythrocytes, also called red blood cells or

red blood corpuscles, are cellular

component of blood, millions of which in the

circulation of vertebrates give the blood its

characteristic colour and carry oxygen from

the lungs to the tissues. The mature human

erythrocyte is small, round, and biconcave; it

appears dumbbell-shaped in profile. The cell

is flexible and assumes a bell shape as it

passes through extremely small blood

vessels. It is covered with a membrane

composed of lipids and proteins, lacks a

nucleus (thus no DNA or RNA), and

contains hemoglobin—a red, iron-rich

protein that binds oxygen. The function of

the red cell and its hemoglobin is to carry

oxygen from the lungs or gills to all the body

tissues and to carry carbon dioxide, a waste

product of metabolism, to the lungs, where it

is excreted. The mammalian erythrocyte is

further adapted by lacking a nucleus—the

amount of oxygen required by the cell for its

own metabolism is thus very low, and most

oxygen carried can be freed into the tissues.

The biconcave shape of the cell allows

oxygen exchange at a constant rate over the

largest possible area. he erythrocyte

develops in bone marrow in several stages:

from a hemocytoblast, a multipotential cell in

the mesenchyme, it becomes an

erythroblast (normoblast); during two to five

days of development, the erythroblast

gradually fills with hemoglobin, and its

nucleus and mitochondria (particles in the

cytoplasm that provide energy for the cell)

disappear. In a late stage the cell is called a

reticulocyte, which ultimately becomes a

fully mature erythrocyte. The average red

cell in humans lives 100–120 days; there are

some 5.2 million red cells per cubic

millimetre of blood in the adult human.

15. In which organelle is ATP found

abundantly?

1 Golgi apparatus

2 Chloroplast

3 Mitochondrion

4 Ribosome

5 Nucleus


Mitochondria and chloroplasts are the

powerhouses of the cell. Mitochondria

appear in both plant and animal cells as

elongated cylindrical bodies, roughly one

micrometre in length and closely packed in

regions actively using metabolic energy.

Mitochondria oxidize the products of

cytoplasmic metabolism to generate

adenosine triphosphate (ATP), the energy

currency of the cell. Chloroplasts are the

photosynthetic organelles in plants and

some algae. They trap light energy and

convert it partly into ATP but mainly into

certain chemically reduced molecules that,

together with ATP, are used in the first steps

of carbohydrate production. Mitochondria

and chloroplasts share a certain structural

resemblance, and both have a somewhat

independent existence within the cell,

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synthesizing some proteins from instructions

supplied by their own DNA.

The Golgi complex is the site of the

modification, completion, and export of

secretory proteins and glycoproteins. This

organelle, first described by the Italian

cytologist Camillo Golgi in 1898, has a

characteristic structure composed of five to

eight flattened, disk-shaped, membrane-

defined cisternae arranged in a stack.

Secretory proteins and glycoproteins, cell

membrane proteins and glycoproteins,

lysosomal proteins, and some glycolipids all

pass through the Golgi structure at some

point in their maturation. In plant cells, much

of the cell wall material passes through the

Golgi as well. As the secretory proteins

move through the Golgi, a number of

chemical modifications may transpire.

Important among these is the modification of

carbohydrate groups. As described above,

many secretory proteins are glycosylated in

the ER. In the Golgi, specific enzymes

modify the oligosaccharide chains of the

glycoproteins by removing certain mannose

residues and adding other sugars, such as

galactose and sialic acid. These enzymes

are known collectively as glycosidases and

glycosyltransferases. Some secretory

proteins will cease to be transported if their

carbohydrate groups are modified incorrectly

or not permitted to form. In some cases the

carbohydrate groups are necessary for the

stability or activity of the protein or for

targeting the molecule for a specific

destination.

Ribosomes are tiny particle that is present in

large numbers in all living cells and serves

as the site of protein synthesis. Ribosomes

occur both as free particles in prokaryotic

and eukaryotic cells and as particles

attached to the membranes of the

endoplasmic reticulum in eukaryotic cells.

Ribosomes can vary in size, although an

average ribosome measures about 200

angstroms in diameter and consists of about

40 percent protein and 60 percent RNA.

Ribosomes are usually made up of three or

four RNA molecules and anywhere from 40

to 80 different proteins. In shape the

ribosome is composed of two subunits, a

larger one and a smaller one, each of which

has a characteristic shape. Ribosomes are

very numerous in a cell and account for a

large proportion of its total RNA. Ribosomes

are the sites at which information carried in

the genetic code is converted into protein

molecules. Ribosomal molecules of

messenger RNA (mRNA) determine the

order of transfer RNA (tRNA) molecules that

are bound to triplets of amino acids

(codons). The order of tRNA molecules

ultimately determines the amino acid

sequence of a protein because molecules of

tRNA catalyze the formation of peptide

bonds between the amino acids, linking

them together to form proteins. The newly

formed proteins detach themselves from the

ribosome site and migrate to other parts of

the cell for use.

The nucleus is a specialized structure

occurring in most cells (except bacteria and

blue-green algae) and separated from the

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rest of the cell by a double layer, the nuclear

membrane. This membrane seems to be

continuous with the endoplasmic reticulum

(a membranous network) of the cell and has

pores, which probably permit the entrance of

large molecules. The nucleus controls and

regulates the activities of the cell (e.g.,

growth and metabolism) and carries the

genes, structures that contain the hereditary

information. Nucleoli are small bodies often

seen within the nucleus; they play an

important part in the synthesis of ribonucleic

acid (RNA) and protein. The gellike matrix in

which the nuclear components are

suspended is the nucleoplasm. A cell

normally contains only one nucleus; under

some conditions, however, the nucleus

divides but the cytoplasm does not. This

produces a multinucleate cell (syncytium)

such as occurs in skeletal muscle fibres.

Some cells—e.g., the human red blood

cell—lose their nuclei upon maturation.

16. Which epidermal tissue in plants

has no cuticle?

1 Lower epidermis of leaf

2 Xylem

3 Epidermal hair

4 Root hair

5 Skin of fruit


The cuticle is the outer layer or part of an

organism that comes in contact with the

environment. In many invertebrates the

dead, noncellular cuticle is secreted by the

epidermis. This layer may, as in the

arthropods, contain pigments and chitin; in

humans the cuticle is the epidermis. In some

higher plants, the cuticle is a water-

impervious protective layer covering the

epidermal cells of leaves, young shoots and

all other aerial plant organs without periderm

and limiting water loss. It consists of cutin, a

waxy, water-repellent substance allied to

suberin, which is found in the cell walls of

corky tissue. Cutin is especially noticeable

on many fruits—e.g., apple, nectarine, and

cherry, which can be buffed to a high gloss.

17. Which gland is not found in the

human skin?

1 Sebaceous glands

2 Talc glands

3 Sweat glands

4 Mammary glands

5 Mucous glands


Talc is a common silicate mineral that is

distinguished from almost all other minerals

by its extreme softness (it has the lowest

rating [1] on the Mohs scale of hardness). Its

soapy or greasy feel accounts for the name

soapstone given to compact aggregates of

talc and other rock-forming minerals. Dense

aggregates of high-purity talc are called

steatite. Since ancient times, soapstones

have been employed for carvings,

ornaments, and utensils; Assyrian cylinder

seals, Egyptian scarabs, and Chinese

statuary are notable examples. Talc is also

13

used in lubricants, leather dressings, toilet

and dusting powders, and certain marking

pencils. It is used as a filler in ceramics,

paint, paper, roofing materials, plastic, and

rubber; as a carrier in insecticides; and as a

mild abrasive in the polishing of cereal

grains such as rice and corn. One of the

remarkable features of talc is its simple,

almost constant composition; talc is a basic

magnesium silicate, Mg3Si4O10(OH)2. Unlike

other silicates, even closely related ones,

talc appears to be unable to accept iron or

aluminium into its structure to form

chemical-replacement series, even though

an iron analogue of talc is known, and the

structurally related chlorite forms at least a

partial series between iron and magnesium

end-members.

The glands of the skin are all exocrine, that

is, they secrete their products, usually

through ducts, to the epidermal surface.

They may be unicellular, as are the goblet

cells of fishes, or multicellular, as are the

sweat glands of humans. Some multicellular

glands are tubular and extrude their

secretion into a central space or lumen;

some, like the oil-producing sebaceous

glands of mammals, form their product by

complete breakdown of the cells, a method

of secretion known as holocrine. Glands

may consist of tubes or sacs, and they may

be singular, clustered, or branched; some

even contain units of more than one type.

They may secrete their product

continuously, periodically, or only once.

Mucous glands secrete a protein called

mucin, which with water forms the

substance known as mucus; this slimy

material serves to lubricate the body, thus

lessening friction and aiding locomotion in

swimming animals. Serous glands produce

a watery secretion; sweat glands of

mammals are of this type. Sebaceous

glands secrete oil, ceruminous glands

secrete wax, mammary glands they are

modified sweat glands!) secrete milk, poison

glands secrete various toxins, and scent

glands secrete a variety of odoriferous

substances. Further, certain epidermal

glands may be modified into light-producing

structures called photophores, seen in the

skin of many deep-sea fishes.

18. Which human vertebrae are fused?

1 Sacral vertebrae

2 Cervical vertebrae

3 Thoracic vertebrae

4 Lumbar vertebrae

5 Atlas and axis


Please refer to the picture below. The

sacrum, (plural Sacra) is the wedge-shaped

triangular bone at the base of the vertebral

column, above the caudal (tail) vertebrae, or

coccyx, that articulates (connects) with the

pelvic girdle. In humans it is usually

composed of five vertebrae, which fuse in

early adulthood. The top of the first

(uppermost) sacral vertebra articulates with

the last (lowest) lumbar vertebra. The

transverse processes of the first three sacral

vertebrae are fused to form wide lateral

14

wings, or alae, and articulate with the

centre-back portions of the blades of the ilia

to complete the pelvic girdle. The sacrum is

held in place in this joint, which is called the

sacroiliac, by a complex mesh of ligaments.

Between the fused transverse processes of

the lower sacral vertebrae, on each side, are

a series of four openings (sacral foramina);

the sacral nerves and blood vessels pass

through these openings. A sacral canal

running down through the centre of the

sacrum represents the end of the vertebral

canal; the functional spinal cord ends at

about the level of the first sacral vertebra,

but its continuation, the filum terminale, can

be traced through the sacrum to the first

coccygeal vertebra.

19. Which is the longest bone in the

human skeleton

1 Femur

2 Humerus

3 Tibia

4 Ulna

5 Fibula


See the diagram below.

Also called the thighbone, the femur is the

upper bone of the leg or hind leg. The head

forms a ball-and-socket joint with the hip (at

the acetabulum), being held in place by a

ligament (ligamentum teres femoris) within

the socket and by strong surrounding

ligaments. In humans the neck of the femur

connects the shaft and head at a 125°

angle, which is efficient for walking. A

15

prominence of the femur at the outside top

of the thigh provides attachment for the

gluteus medius and minimus muscles. The

shaft is somewhat convex forward and

strengthened behind by a pillar of bone

called the linea aspera. Two large

prominences, or condyles, on either side of

the lower end of the femur form the upper

half of the knee joint, which is completed

below by the tibia (shin) and patella

(kneecap). Internally, the femur shows the

development of arcs of bone called

trabeculae that are efficiently arranged to

transmit pressure and resist stress. In

humans, the femur is the longest, most

voluminous, and strongest bone and has

been shown to be capable of resisting

compression forces of 800–1,100 kg (1,800–

2,500 pounds).

The tibia (also called shin) is the inner and

larger of the two bones of the lower leg in

vertebrates—the other is the fibula. In

humans the tibia forms the lower half of the

knee joint above and the inner protuberance

of the ankle below. The upper part consists

of two fairly flat-topped prominences, or

condyles, that articulate with the condyles of

the thighbone, or femur, above. The

attachment of the ligament of the kneecap,

or patella, to the tibial tuberosity in front

completes the knee joint. The lateral condyle

is larger and includes the point at which the

fibula articulates. The tibia's shaft is

approximately triangular in cross section; its

markings are influenced by the strength of

the attached muscles. It is attached to the

fibula throughout its length by an

interosseous membrane.

20. The biological term for middle foot

bones.

1 Phalanges

2 Tarsal bones

3 Carpal bones

4 Metacarpals

5 Metatarsals


The foot is the terminal part of the leg of a

land vertebrate, on which the creature

stands. In most two-footed and many four-

footed animals, the foot consists of all

structures below the ankle joint: heel, arch,

digits, and contained bones such as tarsals,

metatarsals, and phalanges; in mammals

that walk on their toes and in hoofed

16

mammals, it includes the terminal parts of

one or more digits. The major function of the

foot in land vertebrates is locomotion. Three

types of foot posture exist in mammals: (1)

plantigrade, in which the surface of the

whole foot touches the ground during

locomotion (e.g., human, baboon, bear), (2)

digitigrade, in which only the phalanges

(toes, fingers) touch the ground, while the

ankle and wrist are elevated (e.g., dog, cat),

and (3) unguligrade, in which only a hoof

(the tip of one or two digits) touches the

ground—a specialization of running animals

(e.g., horse, deer). In primates the foot, like

the hand, has flat nails protecting the tips of

the digits, and the undersurface is marked

by creases and friction-ridge patterns. In

most primates the foot is adapted for

grasping (i.e., is prehensile), with the first

digit set at an angle from the others. The

foot may be used for manipulation in

addition to its use in climbing, jumping, or

walking. The human foot is nonprehensile

and is adapted for a form of bipedalism

distinguished by the development of the

stride—a long step, during which one leg is

behind the vertical axis of the backbone—

which allows great distances to be covered

with a minimum expenditure of energy.

21. Blood pressure in the arteries is the

highest during….

1 ventricular systole

2 ventricular diastole

3 atrial systole

4 atrial diastole

5 rest period when atria refill


The pressure that develops within the closed

vertebrate circulatory system is highest at

the pump—the heart—and decreases with

distance away from the pump because of

friction within the blood vessels. Because

the blood vessels can change their

diameter, blood pressure can be affected by

both the action of the heart and changes in

the size of the peripheral blood vessels.

Blood is a living fluid—it is viscous and

contains cells (45 percent of its volume in

human beings)—and yet the effects of the

cells on its flow patterns are small. Blood

enters the atrium by positive pressure from

the venous system or by negative pressure

drawing it in by suction. Both mechanisms

operate in vertebrates. Muscular movements

of the limbs and body, and gravity in land

vertebrates, are forces propelling blood to

the heart. In birds and mammals the blood

arrives at the heart with considerable

residual pressure and passes through the

auricles into the ventricles, apparently

without much additional impetus from

contraction of the auricles. The ventricle is

the main pumping chamber, the right and

left ventricles in birds and mammals function

as a volume and a pressure pump,

respectively. The thick muscular wall of the

left ventricle ensures that it develops a

higher pressure during contraction (systole)

in order to force blood through the body. It

follows that pressures in the aorta and

pulmonary artery may be very different. In

17

human beings aortic pressure is about six

times higher.

22. The only artery which carries

deoxygenated blood is the …

1 pulmonary vein

2 vena cava superior

3 pulmonary artery

4 aorta

5 vena cava inferior


An artery is any of the vessels that, with one

exception, carry oxygenated blood and

nourishment from the heart to the tissues of

the body. The exception, the pulmonary

artery, carries oxygen-depleted blood to the

lungs for oxygenation and removal of excess

carbon dioxide. Arteries are muscular and

elastic tubes that must transport blood under

a high pressure exerted by the pumping

action of the heart. The pulse, which can be

felt over an artery lying near the surface of

the skin, results from the alternate

expansion and contraction of the arterial wall

as the beating heart forces blood into the

arterial system via the aorta. Large arteries

branch off from the aorta and in turn give

rise to smaller arteries until the level of the

smallest arteries, or arterioles, is reached.

The threadlike arterioles carry blood to

networks of microscopic vessels called

capillaries, which supply nourishment and

oxygen to the tissues and carry away carbon

dioxide and other products of metabolism by

way of the veins. The largest artery is the

aorta, which arises from the left ventricle of

the heart. The aorta arches briefly upward

before continuing downward close to the

backbone; the arteries that supply blood to

the head, neck, and arms arise from this

arch and travel upward. As it descends

along the backbone, the aorta gives rise to

other major arteries that supply the internal

organs of the thorax. After descending to the

abdomen, the aorta divides into two terminal

branches, each of which supplies blood to

one leg.

23. The valve at the base of the aorta is

the

1 Tricuspid valve

2 Bicuspid valve

3 Semilunar valve

4 Mitral valve

5 Coronary valve


The aorta is the blood vessel (or vessels)

carrying blood from the heart to all the

organs and other structures of the body. At

the opening from the left ventricle into the

aorta is a three-part valve that prevents

backflow of blood from the aorta into the

heart. The aorta emerges from the heart as

the ascending aorta, turns to the left and

arches over the heart (the aortic arch), and

passes downward as the descending aorta.

The left and right coronary arteries branch

from the ascending aorta to supply the heart

muscle. The three main arteries branch from

the aortic arch and give rise to further

18

branches that supply oxygenated blood to

the head, neck, upper limbs, and upper part

of the body. The descending aorta runs

down through the posterior centre of the

trunk past the heart, lungs, and esophagus,

through an opening in the diaphragm, and

into the abdominal cavity. In the heart there

are two valves that prevent backflow of

blood from the ventricles into the atria. On

the right side of the heart is the tricuspid

valve, composed of three flaps of tissue; on

the left is the two-piece mitral valve. Once

blood has left the heart and entered the

aorta, its return is prevented by the

semilunar valves, which consist of

membranous saclike flaps that open away

from the heart. If the flow of blood reverses,

the flaps fill and are pressed against each

other, thus blocking the reentry of blood into

the aorta.

24. The hyphae of Rhizopus (bread

mould) is coenocytic and is

therefore…

1 uninucleate

2 binucleate

3 prokaryote

4 anucleate

5 multinucleate


A coenocyte is a multinucleate cell. It can

result from multiple nuclear divisions without

accompanying cell divisions, or from cellular

aggregation followed by dissolution of the

cell membranes inside the mass.

Coenocytes are found in fungi and some

protists, such as algae and slime mold.

Some plant structures, such as endosperm,

are coenocytic as well.

25. For which animal was the highest

price paid at a game auction during

the 2002/2003 season?

1 Blue crane

2 Buffalo

3 White rhinoceros

4 Black impala

5 Black rhinoceros

Answer: 5 (www.iol.co.za)

This is part of an article that was originally

published on page 4 of The Mercury on

June 18, 2003.

Six black rhinos will be the star attraction at

the 15th Ezemvelo KwaZulu-Natal Wildlife

annual game auction in Hluhluwe-Umfolozi

Park on Saturday. Two years ago, when this

endangered species was last up for auction,

a group of six was sold for R3.3-million -

R550 000 each. Such is their conservation

status that potential black rhino owners must

have their properties inspected by KZN

Wildlife staff before they can register as

bidders. Black rhinos can only be sold to

South African game ranches as trade in the

species between countries is banned under

the Convention on International Trade of

Endangered Species (Cites). Forty white

rhinos are on offer. Top price of R410 000

was paid last year for a female, while the

19

average price was R237 500. Forty-one

nyala - which averaged R7 400 last year -

are also among the animals already

captured and being held in the bomas of the

Centenary Centre in Umfolozi. The prime

purpose of the auction is as a management

tool to dispose of surplus game following

annual scientific evaluation of the animals in

each park managed by KZN Wildlife.

26. Why is the Jacaranda tree a

problem plant?

1 The seeds are poisonous

2 Sap from flowers destroy

paint

3 They uproot roads and walls

4 They displace natural

vegetation

5 They attract a lot of bugs

and mosquitoes

Answer: 4 (Encyclopaedia

Britannica/Wikipedia/IOL)

Jacarandas are a genus under the plant

family Bignoniaceae, especially the two

ornamental trees J. mimosifolia and J.

cuspidifolia. They are widely grown in warm

parts of the world and in greenhouses for

their showy blue or violet flowers and

attractive, oppositely paired, compound

leaves. The genus includes about 50

species native to Central and South America

and to the West Indies. The name jacaranda

is also applied to several tree species of the

genus Machaerium of the pea family

(Leguminosae, or Fabaceae), from which

some of the commercial rosewoods are

obtained. Jacaranda cabinet wood is a

rosewood from the tree species Dalbergia

nigra, also of the pea family. Pretoria in

South Africa is popularly known as The

Jacaranda City due to the enormous number

of Jacaranda trees planted as street trees

and in parks and gardens. In flowering time

the city appears blue/purple in colour when

seen from the nearby hills because of all the

Jacaranda trees. Jacaranda trees are alien

and many alien plants become invasive

outside their places of origin because they

have left behind their natural parasites that

would normally keep their propagation in

check. Thus, invasive alien plants threaten

the indigenous vegetation as they use

valuable and limited water resources. Most

of them use more water than indigenous

plants and are depleting valuable

underground water resources. In 2005, the

city of Pretoria declared war on alien

vegetation and legislated against the

planting or propagation of these. The plants

have been divided into categories - declared

weeds, declared invaders (plants with

commercial value, or plants with ornamental

value). Declared invaders are plants that

must be controlled (removed) on land or

water surfaces by all land users. The

declared invaders are lantana, pom pom

weed, bugweed, azolla, queen of the night,

pampas grass, cat's claw creeper, red

sesbania, yellow oleander, yellow bells and

water hyacinth. These may no longer be

planted or propagated and all trade in their

seeds, cuttings or any other propagation is

20

prohibited. Declared invaders are plants that

pose a threat to the environment but

nevertheless can be exploited for timber,

fruits, fuel wood, medical plants, animal

fodder or building material. The plants

include black wattle, patula pine, sisal, red

eye, grey poplar, watercress, Port Jackson

willow, guava, cluster pine, honey locust and

weeping willow (not to be confused with the

indigenous willow), jacaranda, syringa,

Australian silk oak, St Joseph's lily, sword

fern, tipu tree and New Zealand Christmas

tree. Residents have been urged to learn to

identify and remove invasive alien plants,

join or form a hacking team to remove

invaders and plant indigenous (local) plants

in their garden. The municipality has also

urged residents to buy only indigenous

plants from their local nursery and to replace

the invasive alien plants with an indigenous

plant. Residents should use these methods

to control the invasive plants; uprooting,

felling, cutting, burning, treatment with

registered herbicides, biological control or

any other recognised and appropriate

method.

27. Which one is not a natural gait or

pacing of horses?

1 Walk

2 Trot

3 Canter

4 Gallop

5 Race


The natural gaits of the horse are the walk,

the trot, the canter or slow gallop, and the

gallop, although in dressage the canter and

gallop are not usually differentiated. A riding

horse is trained in each gait and in the

change from one to another. During the walk

and the gallop the horse's head moves

down and forward, then up and back (only at

the trot is it still); riders follow these

movements with their hands. The walk is a

slow, four-beat, rhythmic pace of distinct

successive hoof beats in an order such as

near (left) hind, near fore, off (right) hind, off

fore. Alternately two or three feet may be

touching the ground simultaneously. It may

be a free, or ordinary, walk in which relaxed

extended action allows the horse freedom of

its head and neck, but contact with the

mouth is maintained; or it may be a collected

walk, a short-striding gait full of impulsion, or

vigour; or it may be an extended walk of

long, unhurried strides. The trot is a two-

beat gait, light and balanced, the fore and

hind diagonal pairs of legs following each

other almost simultaneously—near fore, off

hind, off fore, and near hind. Riders can

either sit in the saddle and be bumped as

the horse springs from one diagonal to the

other, or they can rise to the trot, post, by

rising out of the saddle slightly and allowing

more of their weight to bear on the stirrups

when one or the other of the diagonal pairs

of legs leaves the ground. Posting reduces

the impact of the trot on both horse and

rider. As the horse moves faster, its gait

changes into the canter, or ordinary gallop,

in which the rider does not rise or bump. It is

21

a three-beat gait, graceful and elegant,

characterized by one or the other of the

forelegs and both hind legs leading—near

hind, off hind, and near fore practically

together, then off fore, followed briefly by

complete suspension. Cantering can be on

the near lead or the off, depending on which

is the last foot to leave the ground. The

rider's body is more forward than at the trot,

the weight taken by the stirrups. An

accelerated canter becomes the gallop, in

which the rider's weight is brought sharply

forward as the horse reaches speeds up to

30 miles (48 kilometres) an hour. The

horse's movements are the same as in the

canter. To some authorities, the gallop is a

four-beat gait, especially in an extended run.

There are a number of disconnected and

intermediate gaits, some done only by

horses bred to perform them. One is the

rack, a four-beat gait, with each beat evenly

spaced in perfect cadence and rapid

succession. The legs on either side move

together, the hind leg striking the ground

slightly before the foreleg. The single foot is

similar to the rack but slower. In the pace,

the legs on either side move and strike the

ground together in a two-beat gait. The fox

trot and the amble are four-beat gaits, the

latter smoother and gliding.

28. Which one of the following animals

is not listed in the IUCN Red Data

book as threatened?

1 Pelican

2 African Wild Dog

3 African Elephant

4 Jackass Penguin

5 Red-knee Tarantula

Answer: http://www.iucnredlist.org

The IUCN Red List of Threatened Species

(also known as the IUCN Red List or Red

Data List), created in 1963, is the world's

most comprehensive inventory of the global

conservation status of plant and animal

species. The International Union for the

Conservation of Nature and Natural

Resources (IUCN) is the world's main

authority on the conservation status of

species. All the animals listed in the

question have appeared in the IUCN redlist

and the pelican, as of 2001, was largely of

least concern. There are seven or eight

species of water birds constituting the family

Pelecanidae (order Pelecaniformes),

distinguished by their large, elastic throat

pouches. Called pelicans, they inhabit lakes,

rivers, and seacoasts in many parts of the

world. With some species reaching a length

of 180 cm (70 inches), having a wingspan of

3 m (10 feet), and weighing up to 13 kg (30

pounds), they are among the largest of living

birds. The best-known pelicans are the two

species called white pelicans: Pelecanus

erythrorhynchos of the New World, the North

American white pelican, and P. onocrotalus

of the Old World, the European white

pelican. The smaller, 107–137-centimetre

brown pelican (P. occidentalis) of the New

World is a coastal species listed as

endangered by the U.S. Fish and Wildlife

Service. Though the brown pelican once

22

bred in enormous colonies, its population

declined drastically in the period 1940–70 as

a result of DDT and related pesticides. The

birds' breeding subsequently improved after

DDT was banned. In 2001, only the

Dalmatian pelican (Pelecanus crispus) was

listed as vulnerable.

29. Which set of differences between a

plant cell and an animal cell is

correct?

Plant cell Animal cell

1 Has chloroplasts Has chromoplasts

2 Has a vacuole Has no vacuole

3 Has cell wall and

cell membrane

Has only cell wall

4 Has mitochondria Has mitochondria

5 Can

photosynthesise and

respire

Can only respire


A cell is enclosed by a plasma membrane,

which forms a selective barrier that allows

nutrients to enter and waste products to

leave. The interior of the cell is organized

into many specialized compartments, or

organelles, each surrounded by a separate

membrane. One major organelle, the

nucleus, contains the genetic information

necessary for cell growth and reproduction.

Each cell contains only one nucleus,

whereas other types of organelles are

present in multiple copies in the cellular

contents, or cytoplasm. Organelles include

mitochondria, which are responsible for the

energy transactions necessary for cell

survival; lysosomes, which digest unwanted

materials within the cell; and the

endoplasmic reticulum and the Golgi

apparatus, which play important roles in the

internal organization of the cell by

synthesizing selected molecules and then

processing, sorting, and directing them to

their proper locations. In addition, plant cells

contain chloroplasts, which are responsible

for photosynthesis, whereby the energy of

sunlight is used to convert molecules of

carbon dioxide (CO2) and water (H2O) into

carbohydrates. Between all these organelles

is the space in the cytoplasm called the

cytosol. The cytosol contains an organized

framework of fibrous molecules that

constitute the cytoskeleton, which gives a

cell its shape, enables organelles to move

within the cell, and provides a mechanism

by which the cell itself can move. The

cytosol also contains more than 10,000

different kinds of molecules that are involved

in cellular biosynthesis, the process of

making large biological molecules from

small ones.

30. When a piece of liver is put in

hydrogen peroxide, oxygen is given

off. The chemical in the liver that is

responsible for the reaction is….

1 a hormone

2 an enzyme

3 an acid

4 a buffer

5 alcohol

23


The enzyme responsible for this reaction

(hydrogen peroxide decomposition to water

and oxygen) is called catalase. Found

extensively in mammalian tissues, catalase

prevents the accumulation of and protects

the body tissues from damage by peroxide,

which is continuously produced by

numerous metabolic reactions. All known

animals use catalase in every organ, with

particularly high concentrations occurring in

the liver. One unique use of catalase occurs

in bombardier beetle. The beetle has two

sets of chemicals ordinarily stored

separately in its paired glands. The larger of

the pair, the storage chamber or reservoir,

contains hydroquinones and hydrogen

peroxide, whereas the smaller of the pair,

the reaction chamber, contains catalases

and peroxidases. To activate the spray, the

beetle mixes the contents of the two

compartments, causing oxygen to be

liberated from hydrogen peroxide. The

oxygen oxidizes the hydroquinones and also

acts as the propellant. A rare hereditary

metabolic disorder caused by lack of the

enzyme catalase is called acatalasia.

Although a deficiency of catalase activity is

noted in many tissues of the body, including

the red blood cells, bone marrow, liver, and

skin, only about half of the affected persons

have symptoms, which consist of recurrent

infections of the gums and associated oral

structures that may lead to gangrenous

lesions. Such lesions are rare after puberty.

The disorder has been most frequently

reported in Japanese and Korean

populations; its estimated frequency in

Japan is approximately 2 in 100,000.

31. Bacteria and algae are classified as

plants because they….

1 are green

2 have cell walls

3 can produce their own food

4 survive in the form of seed

and not in eggs

5 cannot move


Bacteria and algae are not classified as

plants but have some similarities to them.

Bacteria, archaebacteria, and blue-green

algae are prokaryotes and fall under the

kingdom Monera. Archaebacteria are

unicellular organisms that are prokaryotic

(that is, do not have a membrane-bound

nucleus and other internal units) but that

differ in certain physiological and genetic

features from bacteria, the most prominent

prokaryotes. Archaea have some features in

common with bacteria as well as eukaryotes

(organisms whose cells contain nuclear

membranes), but evidence suggests that

archaea are more closely related to

eukaryotes than to bacteria

The blue-green algae, also called

cyanobacteria, are traditionally placed with

the other algae (e.g., seaweeds) and are

studied more by botanists than by

microbiologists. Blue-green algae may be

either unicellular or filamentous, and they

24

behave like true plants, photosynthesizing in

a way that resembles green plants rather

than bacteria. Many move by gliding, as do

some bacteria and some true unicellular

algae. They are often extremely abundant

around hot springs or at the edges of muddy

ponds, and, though they are resistant to

harsh environments, blue-green algae are

killed by many drugs (e.g., antibiotics) used

against bacteria. Perhaps they are best

regarded as representing a group close to

the main evolutionary line that gave rise to

the eukaryotic plants.

32. The origin of the basic component of

all organic compounds is….

1 CO2

2 H2O

3 O2

4 N2

5 glucose


During photosynthesis in green plants, light

energy is captured and used to convert

water, carbon dioxide, and minerals into

oxygen and energy-rich organic compounds.

In chemical terms, photosynthesis is a light-

energized oxidation–reduction process.

(Oxidation refers to the removal of electrons

from a molecule; reduction refers to the gain

of electrons by a molecule.) In plant

photosynthesis, the energy of light is used to

drive the oxidation of water (H2O), producing

oxygen gas (O2), hydrogen ions (H+), and

electrons. Most of the removed electrons

and hydrogen ions ultimately are transferred

to carbon dioxide (CO2), which is reduced to

organic products. Other electrons and

hydrogen ions are used to reduce nitrate

and sulfate to amino and sulfhydryl groups

in amino acids, which are the building blocks

of proteins. In most green cells,

carbohydrates—especially starch and the

sugar sucrose—are the major direct organic

products of photosynthesis. The overall

reaction in which carbohydrates—

represented by the general formula

(CH2O)—are formed during plant

photosynthesis can be indicated by the

following equation:

33. Plants do not react to the stimulus

of…

1 light

2 water

3 gasses

4 touch

5 gravity


No experiment can prove that plants grow

towards a gas as the gas will have to be

contained within an impervious medium, yet

the plant will have to sense its presence in

order to grow away from or towards it! The

response or orientation of a plant or certain

lower animals to a stimulus that acts with

greater intensity from one direction than

another is called tropism. It may be achieved

by active movement or by structural

25

alteration. Forms of tropism include

phototropism (response to light), geotropism

(response to gravity), chemotropism

(response to particular substances),

hydrotropism (response to water),

thigmotropism (response to mechanical

stimulation), traumatotropism (response to

wound lesion), and galvanotropism, or

electrotropism (response to electric current).

Most tropic movements are orthotropic; i.e.,

they are directed toward the source of the

stimulus. Plagiotropic movements are

oblique to the direction of stimulus. Diatropic

movements are at right angles to the

direction of stimulus.

Plants respond to a variety of external

stimuli by utilizing hormones as controllers in

a stimulus-response system. Directional

responses of movement are known as

tropisms and are positive when the

movement is toward the stimulus and

negative when it is away from the stimulus.

When a seed germinates, the growing stem

turns upward toward the light, and the roots

turn downward away from the light. Thus,

the stem shows positive phototropism and

negative geotropism, while the roots show

negative phototropism and positive

geotropism. In this example, light and gravity

are the stimuli, and directional growth is the

response. The controllers are certain

hormones synthesized by cells in the tips of

the plant stems. These hormones, known as

auxins, diffuse through the tissues beneath

the stem tip and concentrate toward the

shaded side, causing elongation of these

cells and, thus, a bending of the tip toward

the light. The end result is the maintenance

of the plant in an optimal condition with

respect to light.

34. Which one is not part of a flower?

1 Petal

2 Anther

3 Sepal

4 Seeds

5 Ovary


Seeds are found in ripened ovaries, long

after the flower has disappeared. A flower is

the reproductive portion of any plant in the

division Magnoliophyta (Angiospermae),

commonly called flowering plants or

angiosperms. As popularly used, the term

“flower” especially applies when part or all of

the reproductive structure is distinctive in

colour and form. Basically, each flower

consists of a floral axis upon which are

borne the essential organs of reproduction

(stamens and pistils) and usually accessory

organs (sepals and petals); the latter may

serve to both attract pollinating insects and

protect the essential organs. The floral axis

is a greatly modified stem; unlike vegetative

stems, which bear leaves, it is usually

contracted, so that the parts of the flower

are crowded together on the stem tip, the

receptacle. The flower parts are usually

arrayed in whorls (or cycles) but may also

be disposed spirally, especially if the axis is

elongate. There are commonly four distinct

whorls of flower parts: (1) an outer calyx

26

consisting of sepals; within it lies (2) the

corolla, consisting of petals; (3) the

androecium, or group of stamens; and in the

centre is (4) the gynoecium, consisting of

the pistils. The sepals and petals together

make up the perianth, or floral envelope.

The sepals are usually greenish and often

resemble reduced leaves, while the petals

are usually colourful and showy. Sepals and

petals that are indistinguishable, as in lilies

and tulips, are sometimes referred to as

tepals. The androecium, or male parts of the

flower comprise the stamens, each of which

consists of a supporting filament and an

anther, in which pollen is produced. The

gynoecium, or female parts of the flower,

comprise the pistils, each of which consists

of an ovary, with an upright extension, the

style, on the top of which rests the stigma,

the pollen-receptive surface. The ovary

encloses the ovules, or potential seeds. A

pistil may be simple, made up of a single

carpel, or ovule-bearing modified leaf; or

compound, formed from several carpels

joined together. A flower having sepals,

petals, stamens, and pistils is complete;

lacking one or more of such structures, it is

said to be incomplete. Stamens and pistils

are not present together in all flowers. When

both are present the flower is said to be

perfect, or bisexual, regardless of a lack of

any other part that renders it incomplete

(see photograph). A flower that lacks

stamens is pistillate, or female, while one

that lacks pistils is said to be staminate, or

male. When the same plant bears unisexual

flowers of both sexes, it is said to be

monoecious (e.g., tuberous begonia, hazel,

oak, corn); when the male and female

flowers are on different plants, the plant is

dioecious (e.g., date, holly, cottonwood,

willow); when there are male, female, and

bisexual flowers on the same plant, the plant

is termed polygamous.

35. Which one is not a fruit?

1 Tomato

2 Pumpkin

3 Green Pepper

4 Nuts

5 Green beans


An uneducated guess would list nuts as the

answer but this question is in fact invalid

since there is no correct answer! In its strict

botanical sense, a fruit is the fleshy or dry

ripened ovary of a plant, enclosing the seed

or seeds. Thus, apricots, bananas, and

grapes, as well as bean pods, corn grains,

tomatoes, cucumbers, and (in their shells)

acorns and almonds, are all technically

fruits. Popularly, however, the term is

restricted to the ripened ovaries that are

sweet and either succulent or pulpy.

36. Which factor is not needed for the

germination of seeds?

1 Water

2 Light

3 Oxygen

4 Heat

27

5 Growth medium


Germination is the sprouting of a seed,

spore, or other reproductive body, usually

after a period of dormancy. Seed

germination depends on many factors, both

internal and external. The most important

external factors include: water, oxygen,

temperature, light (for many plants the least

critical in the early stages) and the correct

soil conditions. Every variety of seed

requires a different set of variables for

successful germination. This depends

greatly on the individual seed variety and is

closely linked to the ecological conditions in

the plants' natural habitat. Germination

sometimes occurs early in the development

process; the mangrove (Rhizophora)

embryo develops within the ovule, pushing

out a swollen rudimentary root through the

still-attached flower. In peas and corn

(maize), the cotyledons (seed leaves)

remain underground; in other species

(beans, sunflowers, etc.), the hypocotyl

(embryonic stem) grows several inches

above the ground, carrying the cotyledons

into the light, in which they become green

and often leaf-like.

37. Lichens are the symbiotic

relationship between….

1 fungi and algae

2 mosses and fungi

3 algae and mosses

4 algae and bacteria

5 mosses and bacteria


A lichen is any of about 15,000 species of

thallophytic plantlike organisms that consist

of a symbiotic association of algae (usually

green) and fungi (mostly ascomycetes and

basidiomycetes). Lichens were once

classified as single organisms until the

advent of microscopy, when the association

of algae and fungi became evident. There is

still some discussion about how to classify

lichens. Lichens have been used by humans

as food and as sources of medicine and

dye. They also provide two-thirds of the food

supply for the caribou and reindeer that

roam the far northern ranges. The

composite body of a lichen is called a thallus

(plural thalli). The homoeomerous type of

thallus consists of numerous algal cells

(called the phycobionts) distributed among a

lesser number of fungal cells (called the

mycobionts). The heteromerous thallus

differs in that it has a predominance of

fungal cells. Hairlike growths that anchor the

thallus to its substrate are called rhizines.

Lichens that form a crustlike covering that is

thin and tightly bound to the substrate are

termed crustose. Squamulose lichens are

small and leafy with loose attachments to

the substrate. Foliose lichens are large and

leafy, reaching diameters of several feet in

some species, and are usually attached to

the substrate by their large, plate-like thalli

at the centre.

38. What does coral consist of?

28

1 Skeletons of dead fish

2 Small animals’ calcium

carbonate exoskeletons

3 Minerals excreted by

decomposers

4 Silica deposited by small

animals

5 Deposits from a saturated

sea salt solution


A coral is any of a variety of invertebrate

marine organisms of the class Anthozoa

(phylum Cnidaria) that are characterized by

skeletons—external or internal—of a stone-

like, horny, or leathery consistency. The

term coral is also applied to the skeletons of

these animals, particularly to those of the

stone-like corals. Stony corals (order

Madreporaria or Scleractinia) number about

1,000 species; black corals and thorny

corals (Antipatharia), about 100 species;

horny corals, or gorgonians (Gorgonacea),

about 1,200 species; and blue corals

(Coenothecalia), one living species. The

body of a coral animal consists of a polyp—

a hollow, cylindrical structure attached at its

lower end to some surface. At the free end

is a mouth surrounded by tentacles. The

tentacles, which gather food, are more or

less extensible and are armed with

specialized stinging structures called

nematocysts that paralyze prey. Eggs and

sperm, usually produced by separate

individuals, develop as outgrowths in the

gastrovascular cavity and are expelled

through the mouth into the open water.

Fertilization usually takes place in the water

but sometimes occurs in the gastrovascular

cavity. The larva, a ciliated form known as a

planula, swims about for several days or as

long as several weeks, then settles onto a

solid surface and develops into a polyp.

Reproduction also occurs by budding. The

bud remains attached to the original polyp. A

colony develops by the constant addition

and growth of new buds. As new polyps

develop, the old ones beneath die, but the

skeletons remain.

39. Where did American Indians obtain

poison for their arrow tips?

1 A kind of frog

2 Venomous snakes

3 Butterflies which are

poisonous

4 Poisonous plants and

berries

5 Scorpions


Anura (also called Salientia) is one of the

major extant orders of the class Amphibia. It

includes the frogs and toads, which,

because of their wide distribution, are known

by most people around the world. The name

frog is commonly applied to those forms with

long legs and smooth, mucus-covered skins,

toad being used for a variety of robust,

short-legged anurans, especially those with

rough skins. The name toad is applied so

unevenly that one member of a family may

29

be called a toad and a closely related

member a frog. The familiar members of the

family Bufonidae may be distinguished as

“true toads.” Frogs are used as teaching

tools from grade school through college.

People in various parts of the world eat frog

legs, and some kinds of toads are used in

insect control. Certain South American

Indians use the poisonous secretions of

some kinds of frogs for poison arrows and

now biochemists are studying the possible

medical uses of the constituents of the

poison. The frog commonly used for poison

harvest is the poison dart frog or poison

arrow frog which are vividly coloured,

poisonous frogs of the American tropics.

Arrow-poison frogs are tiny, usually

measuring only 1–5 cm (0.5–2 inches) long,

but very conspicuous, coloured in

combinations of black with bright red, yellow,

pink, orange, green, and blue. They live on

or near the ground, and all are members of

the family Dendrobatidae, but not all the 170

frog species in this family are toxic. Arrow-

poison frogs possess some of the most

potent toxins known. Poison glands

scattered all over the amphibians' bodies

produce alkaloids that affect the nervous

system. The most toxic species recorded is

the bright yellow Phyllobates terribilis of

Colombia, capable of injuring a person who

merely touches it. The poison can be

absorbed through unbroken skin and causes

severe irritation. Local people do not kill this

frog to extract its poison but merely scrape

their blowgun darts across its back before

releasing the amphibian. Other arrow-poison

frogs are not as fortunate. Several

Colombian tribes use different frog species

to provide the poisons with which they tip

their blowgun darts. The Chocó people force

a sharp stick into the frog's mouth and hold

it over a fire until it releases a white froth of

toxic alkaloids. One frog can provide enough

secretion to dip 50 darts, which will remain

potent for a year. The bright colours

advertising their poisons allow these frogs to

hunt boldly by day, feeding on ants,

termites, and other small creatures living in

the leaf litter of the tropical rainforest.

40. Starch and saliva re mixed at a

temperature of 37 ºC and tested

with iodine solution. Which colour

can be observed?

1 Blue-black

2 Brown-yellow

3 Blue

4 Purple

5 Pink


Saliva contains salivary amylase, a member

of a class of enzymes that catalyze the

hydrolysis (splitting of a compound by

addition of a water molecule) of starch into

smaller carbohydrate molecules such as

maltose (a molecule composed of two

glucose molecules). Two categories of

amylases, denoted alpha and beta, differ in

the way they attack the bonds of the starch

molecules. Alpha amylase is widespread

among living organisms. In the digestive

30

systems of humans and many other

mammals, an alpha-amylase called ptyalin

is produced by the salivary glands, whereas

pancreatic amylase is secreted by the

pancreas into the small intestine. Ptyalin is

mixed with food in the mouth, where it acts

upon starches. Although the food remains in

the mouth for only a short time, the action of

ptyalin continues for up to several hours in

the stomach—until the food is mixed with

the stomach secretions, the high acidity of

which inactivates ptyalin. Ptyalin's digestive

action depends upon how much acid is in

the stomach, how rapidly the stomach

contents empty, and how thoroughly the

food has mixed with the acid. Under optimal

conditions as much as 30 to 40 percent of

ingested starches can be broken down to

maltose by ptyalin during digestion in the

stomach.

After incubation, there will be no starch left

since it will have all been broken down to

maltose by the action of salivary amylase.

Thus, since iodine only detects amylase

(starch), the colour of the added iodine

solution will persist, i.e., there will be no

colour change on its part.

41. What is the main function of the cilia

in the respiratory tract of humans?

They….

1 promote the liberation of

carbon dioxide

2 secrete mucus

3 remove mucus

4 enlarge the surface area for

gaseous exchange

5 moisten and warm the

incoming air


Cilia are short eyelash-like filaments that are

numerous on tissue cells of most animals

and provides the means for locomotion of

protozoans of the phylum Ciliophora. Cilia

may be fused in short transverse rows to

form membranelles or in tufts to form cirri.

Capable of beating in unison, cilia move

mammalian ova through oviducts, generate

water currents to carry food and oxygen past

the gills of clams, carry food through the

digestive systems of snails, circulate

cerebrospinal fluid of animals, and clean

debris from the respiratory systems of

mammals. The respiratory tract is covered in

an epithelium, the type of which varies down

the tract. There are glands and mucus

produced by goblet cells in parts, as well as

smooth muscle, elastin or cartilage. Most of

the epithelium (from the nose to the bronchi)

is covered in pseudostratified columnar

ciliated epithelial cells, commonly called

respiratory epithelium. The cilia beat in one

direction, moving mucus towards the throat

where it is swallowed. Moving down the

bronchioles, the cells get more cuboidal in

shape but are still ciliated.

In modified form, cilia trigger the discharge

of stinging devices in jellyfish and give rise

to the light-sensitive rods of the mammalian

retina and the odour-detecting units of

olfactory neurons.

31

42. Which fact about photosynthesis is

incorrect?

1 Water, CO2, chlorophyll and

sunlight are mainly needed

2 It takes place in the grana,

in the chloroplasts, in the

palisade cells and in the

mesophyll in a leaf

3 Some plants

photosynthesise at 5 ºC and

others at 70 ºC

4 The two biochemical

phases are glycolysis and

the Krebbs cycle

5 Products of photosynthesis

are oxygen, glucose,

sucrose and starch


During photosynthesis in green plants, light

energy is captured and used to convert

water, carbon dioxide, and minerals into

oxygen and energy-rich organic compounds.

In chemical terms, photosynthesis is a light-

energized oxidation–reduction process.

(Oxidation refers to the removal of electrons

from a molecule; reduction refers to the gain

of electrons by a molecule.) In plant

photosynthesis, the energy of light is used to

drive the oxidation of water (H2O), producing

oxygen gas (O2), hydrogen ions (H+), and

electrons. Most of the removed electrons

and hydrogen ions ultimately are transferred

to carbon dioxide (CO2), which is reduced to

organic products. Other electrons and

hydrogen ions are used to reduce nitrate

and sulfate to amino and sulfhydryl groups

in amino acids, which are the building blocks

of proteins. In most green cells,

carbohydrates—especially starch and the

sugar sucrose—are the major direct organic

products of photosynthesis. The overall

reaction in which carbohydrates—

represented by the general formula

(CH2O)—are formed during plant

photosynthesis can be indicated by the

following equation:

43. Which one is not a function of the

kidney?

1 Osmoregulation

2 Regulates the pH of blood

3 Filtration of metabolic waste

products from the blood

4 Regulates the salt content

of blood

5 Regulates the glucose level

in the blood


Kidneys have evolved in multicellular

animals as a highly sophisticated channel

for waste disposal, and they function to

regulate the levels of water, salts, and

organic materials in the bodies of higher

animals. Materials eliminated via the kidney

include nitrogenous waste products

(ammonia, uric acid, urea, creatine,

creatinine, and amino acids), excess

32

quantities of salts and water that may be

taken into the body, and various other

organic materials produced by life-sustaining

chemical reactions. Functionally, the kidney

is a microfilter that initially removes

dissolved as well as some suspended

materials from the circulatory system, along

with large quantities of water. These

substances are differentially reabsorbed into

the blood by various kidney structures

during urine formation to a degree that

varies considerably throughout the animal

kingdom. For example, animals that absorb

large quantities of water into their bodies

(such as freshwater fishes) excrete copious

quantities of water in their urine. The reverse

is true of many desert animals, who must

conserve water and therefore produce a

thick, semisolid urine. The kidney, in its

various stages of evolution, functions at the

expense of considerable metabolic energy

and cannot be considered to be a passive

system.

44. The figure below shows details of an

experiment in which three similar

table cloths (1, 2 and 3) with

identical fat stains were washed in

the same washing machine with the

same enzyme-containing washing

powder at three different

temperatures.

Before theywere washed

After washing for 15 minutes

1 2 3

fat stain

15 oC 37 oC 60 oC

What can be concluded after

studying the results?

1 Enzymes are substrate

specific

2 Enzymes are sensitive to

temperature

3 Not enough washing

powder was used

4 Cloths were not washed

long enough

5 pH ahs no influence on this

enzyme


All washing conditions were kept identical,

with temperature being the only variable. At

15 ºC, the fat stain was only partially

removed, at 37 ºC it was completely

removed whilst at 60 ºC it was not removed

at all. This shows that the enzyme employed

has an optimum temperature of 37 ºC.

Enzymes catalyze all aspects of cell

metabolism. This includes the digestion of

food, in which large nutrient molecules (such

as proteins, carbohydrates, and fats) are

broken down into smaller molecules; the

conservation and transformation of chemical

energy; and the construction of cellular

macromolecules from smaller precursors.

33

Many inherited human diseases, such as

albinism, result from a deficiency of a

particular enzyme. Enzymes also have

valuable industrial and medical applications.

The fermenting of wine, leavening of bread,

curdling of cheese, and brewing of beer

have been practiced from earliest times, but

not until the 19th century were these

reactions understood to be the result of the

catalytic activity of enzymes. Since then,

enzymes have assumed an increasing

importance in industrial processes that

involve organic chemical reactions. The

uses of enzymes in medicine include killing

disease-causing microorganisms, promoting

wound healing, and diagnosing certain

diseases. Enzyme activity can be affected

by other molecules. Inhibitors are molecules

that decrease enzyme activity; activators are

molecules that increase activity. Many drugs

and poisons are enzyme inhibitors. Activity

is also affected by temperature, chemical

environment (e.g. pH), and the

concentration of substrate. Some enzymes

are used commercially, for example, in the

synthesis of antibiotics. In addition, some

household products use enzymes to speed

up biochemical reactions (e.g., enzymes in

biological washing powders break down

protein or fat stains on clothes; enzymes in

meat tenderizers break down proteins,

making the meat easier to chew).

45. Which one does not have sensory

receptors?

1 Retina in the eye

2 Olfactory cells in the nose

3 Corpuscles of Langerhans

in the skin

4 Taste buds

5 Organ of Corti in the

cochlea of the ear


Organisms have a variety of sensory

structures that respond to different stimuli,

such as light, pressure, or chemicals, all of

which are forms of energy. Once excited,

these sensory receptors convert the energy

of the stimulus into a behavioral response of

the organism. In general, sense cells, or

receptors, located superficially in an

organism receive signals from outside the

organism and are parts of the exteroceptive

system. Receptors located inside the body

receive signals from changes taking place

inside the body and belong to the

interoceptive system. On activation, sensory

cells cause reactions appropriate to their

location; they are said to respond with their

local sign. Photoreceptors are sensitive to

light changes. They contain photopigments

for absorption of light. The variety of

photopigments in different cells determines

the number of colours that can be

distinguished. It is interesting to note that in

insects, among other animals, colour

sensitivity is extended into the ultraviolet

range, though it is short in the red range.

Cells especially sensitive to infrared

radiation are found in the remarkable pit

organs of vipers, which enable the snake to

34

locate warm-blooded prey from a distance

even when it freezes into immobility.

In the skin of warm-blooded animals, nerve

endings, with or without accessory

structures, are present that react especially

to warming or to cooling. Well-known organs

of chemical reception are those of smell and

of taste. Except in cases in which there is

great specificity to one substance, as, for

example, the sex attractant in insects, the

spectrum of chemoreceptive cells is broad.

The sense of taste was long thought to be

mediated by narrow, separate fibres for acid,

bitter, sweet, and sour sensations; this

viewpoint is now being replaced by one in

which the spectra are considerably wider.

Frogs have been shown to have taste cells

that react specifically to distilled water.

Chemoreceptors are also present as

interoceptors, a well-known example being

the carotid body in certain vertebrates; this

organ monitors oxygen pressure in the

carotid artery, which supplies the brain with

blood. Mechanoreceptors are the most

widespread type of sense receptor and the

most varied with regard to localization,

sensitivity, and type of nerve-impulse firing.

There are numerous subdivisions of the

mechanoreceptive sense, such as touch,

pain, sound, gravity, and muscle tone.

Examples in humans include the naked

nerve endings in the cornea of the eye; the

Pacinian corpuscles in the skin, with their

multilayered sheath-like covers; and the hair

cells in the inner ear. Impulse formation may

continue for as long as stimulus lasts, thus

giving a continuous (tonic) type of discharge,

or be limited and proportional to the rate of

change of the stimulus, thus producing an

abrupt (phasic) discharge. A remarkable

type of mechanoreceptor occurs in the

elastic organs of crustacean legs;

movement-sensitive cells fire for the time a

joint moves in one direction, and others fire

for the opposite movement.

In addition to melanocytes, human

epidermis contains another system of

dendritic cells called Langerhans cells (after

their discoverer, the German physician Paul

Langerhans, in 1868) which do not

manufacture pigment. Their distribution

extends farther toward the skin surface than

that of the pigment cells. Their function

remained obscure until it was realized that

they are a vital part of the immunologic

mechanism. Langerhans cells can be looked

upon as “sentinel” cells of the immune

system. By virtue of their situation, they are

among the first cells to come into contact

with foreign particulate substances

encountering the skin. Their function is

aided by the large surface area created by

the dendritic processes of the cell. By

means of specialized receptors on the cell

membrane, the Langerhans cell recognizes

invading as opposed to host molecules. By

conveying this information to the lymphoid

system, the body is able to mount a

defensive immunologic response to the

foreign material.

46. Which hormone is responsible for

the development of the placenta

during pregnancy in mammals?

35

1 Oestrogen

2 Adrenalin

3 Insulin

4 Progesterone

5 Follicle Stimulating

Hormone (FSH)


Estrogen is any of a group of hormones that

primarily influence the female reproductive

tract in its development, maturation, and

function. There are three major hormones—

estradiol, estrone, and estriol—among the

estrogens, estradiol being the predominant

one. The major sources of estrogens are the

ovaries and the placenta (the temporary

organ that serves to nourish the fetus and

remove its wastes); additional small

amounts are secreted by the adrenal glands

and by the male testes. It is believed that the

egg follicle (the saclike structure that holds

the immature egg) and interstitial cells

(certain cells in the framework of connective

tissue) in the ovary are the actual production

sites of estrogens in the female. Estrogen

levels in the bloodstream seem to be highest

during the egg-releasing period (ovulation)

and after menstruation, when tissue called

the corpus luteum replaces the empty egg

follicle. Estrogens affect the ovaries, vagina,

fallopian tubes, uterus, and mammary

glands. In the ovaries, estrogens help to

stimulate the growth of the egg follicle; they

also stimulate the pituitary gland in the brain

to release hormones that assist in follicular

development. Once the egg is released, it

travels through the fallopian tubes on its way

to the uterus; in the fallopian tubes

estrogens are responsible for developing a

thick muscular wall and for the contractions

that transport the egg and sperm cells. The

young female uterus, if deprived of

estrogens, does not develop into its adult

form; the adult uterus that does not receive

estrogens begins to show tissue

degeneration. Estrogens essentially build

and maintain the endometrium—a mucous

membrane that lines the uterus; they

increase the endometrium's size and weight,

cell number, cell types, blood flow, protein

content, and enzyme activity. Estrogens also

stimulate the muscles in the uterus to

develop and contract; contractions are

important in helping the wall to slough off

dead tissue during menstruation and during

the delivery of a child and of the placenta.

The cervix, the tip of the uterus, which

projects into the vagina, secretes mucus that

enhances sperm transport; estrogens are

thought to regulate the flow and thickness of

the mucous secretions. The growth of the

vagina to its adult size, the thickening of the

vaginal wall, and the increase in vaginal

acidity that reduces bacterial infections are

also correlated to estrogen activities. In the

breasts the actions of estrogens are

complexly interrelated with those of other

hormones, and their total significance is not

easily defined; they are, however,

responsible for growth of the breasts during

adolescence, pigmentation of the nipples,

and the eventual cessation of the flow of

milk. Estrogens also influence the structural

36

differences between the male and female

bodies. Usually the female bones are

smaller and shorter, the pelvis is broader,

and the shoulders are narrower. The female

body is more curved and contoured because

of fatty tissue that covers the muscles,

breasts, buttocks, hips, and thighs. The

body hair is finer and less pronounced, and

the scalp hair is usually more permanent.

The voice box is smaller and the vocal cords

shorter, giving a higher-pitched voice in

females than in males. In addition,

estrogens suppress the activity of

sebaceous (oil-producing) glands and

thereby reduce the likelihood of acne in the

female.

Progesterone is the hormone secreted by

the female reproductive system that

functions mainly to regulate the condition of

the inner lining (endometrium) of the uterus.

Progesterone is produced by the ovaries,

placenta, and adrenal glands; in the ovaries

the site of production is the corpus luteum

tissue, which begins to form prior to an egg's

release and continues to grow into the

empty follicular space once the egg has left

the follicle (a capsule of tissue around the

egg). The released egg, if it is fertilized by

the male sperm cell, becomes implanted in

the uterus, and a placenta forms. The

placenta then produces progesterone during

the period of pregnancy. If the egg is not

fertilized, progesterone is secreted by the

ovaries until a few days before

menstruation, at which time the level of

progesterone drops sufficiently to stop the

growth of the uterine wall and to cause it to

start to break down, and menstruation

ensues. Progesterone prepares the wall of

the uterus so that the lining is able to accept

a fertilized egg and so that the egg can be

implanted and develop. It also inhibits

muscular contractions of the uterus that

would probably cause the wall to reject the

adhering egg.

The follicle stimulating hormone (FSH) is

one of two gonadotropic hormones (i.e.,

hormones concerned with the regulation of

the activity of the gonads, or sex glands)

produced by the pituitary gland. FSH, a

glycoprotein operating in conjunction with

luteinizing hormone (LH), stimulates

development of the graafian follicle, a small,

egg-containing vesicle in the ovary of the

female mammal; in the male, it promotes the

development of the tubules of the testes and

the differentiation of sperm. Though in the

male the presence of FSH is necessary for

the maturation of spermatozoa, additional

FSH may not be required for months

because testosterone can maintain this

activity. In the female, however, there is a

rhythmic, or cyclical, increase and decrease

of FSH, which is essential for monthly

ovulation.

Adrenaline (also called epinephrine) is a

hormone secreted by the medulla of the

adrenal glands which are either of two small

triangular endocrine glands that are located

above each kidney. Adrenaline stimulates

the breakdown of glycogen to glucose in the

liver, which results in the raising of the level

of blood sugar. Both hormones increase the

level of circulating free fatty acids. The extra

37

amounts of glucose and fatty acids can be

used by the body as fuel in times of stress or

danger where increased alertness or

exertion is required. Epinephrine is

sometimes called the emergency hormone

because it is released during stress and its

stimulatory effects fortify and prepare an

animal for either “fight or flight.”

Insulin is a hormone that regulates the level

of sugar (glucose) in the blood and is

produced by the beta cells of the islets of

Langerhans in the pancreas. Insulin is

secreted when the level of blood glucose

rises—as after a meal. When the level of

blood glucose falls, secretion of insulin

stops, and the liver releases glucose into the

blood. Insulin is a simple protein in which

two polypeptide chains of amino acids are

joined by disulfide linkages. Insulin helps

transfer glucose into cells so that they can

oxidize the glucose to produce energy for

the body. In adipose (fat) tissue, insulin

facilitates the storage of glucose and its

conversion to fatty acids. In muscle it

promotes the uptake of amino acids for

making proteins. In the liver it helps convert

glucose into glycogen and it decreases

gluconeogenesis (the formation of glucose

from noncarbohydrate sources). Inadequate

production of insulin is responsible for the

condition called diabetes mellitus.

47. The part of the brain that is used in

the answering of this question.

1 Cerebrum

2 Cerebellum

3 Hypothalamus

4 Medulla oblongata

5 Pons Varolii


The human brain weighs about 1,500 grams

(3 pounds) and constitutes about 2 percent

of total body weight. It consists of three

major divisions: (1) the massive paired

hemispheres of the cerebrum, (2) the

brainstem, consisting of the thalamus,

hypothalamus, epithalamus, subthalamus,

midbrain, pons, and medulla oblongata, and

(3) the cerebellum. The cerebrum, derived

from the telencephalon, is the largest,

uppermost portion of the brain. It is involved

with sensory integration, control of voluntary

movement, and higher intellectual functions,

such as speech and abstract thought.

The cerebellum (“little brain”) overlies the

posterior aspect of the pons and medulla

oblongata and fills the greater part of the

posterior fossa of the skull. This distinctive

part of the brain is derived from the rhombic

lips, thickenings along the margins of the

embryonic hindbrain. It consists of two

paired lateral lobes, or hemispheres, and a

midline portion known as the vermis. The

cerebellar cortex appears very different from

the cerebral cortex in that it consists of small

leaflike laminae called folia. The cerebellum

functions as a kind of computer, providing a

quick and clear response to sensory signals.

It plays no role in sensory perception, but it

exerts profound influences upon equilibrium,

muscle tone, and the coordination of

38

voluntary motor function. Because the input

and output pathways both cross, a lesion of

a lateral part of the cerebellum will have an

ipsilateral effect on coordination.

The hypothalamus lies below the thalamus

in the walls and floor of the third ventricle. It

is divided into medial and lateral groups by a

curved bundle of axons called the fornix,

which originate in the hippocampal formation

and project to the mammillary body. The

hypothalamus controls major endocrine

functions by secreting hormones (i.e.,

oxytocin and vasopressin) that induce

smooth muscle contractions of the

reproductive, digestive, and excretory

systems; other neurosecretory neurons

convey hormone-releasing factors (e.g.,

growth hormone, corticosteroids, thyrotropic

hormone, and gonadotropic hormone) via a

vascular portal system to the

adenohypophysis, a portion of the pituitary

gland. Specific regions of the hypothalamus

are also involved with the control of

sympathetic and parasympathetic activities,

temperature regulation, food intake, the

reproductive cycle, and emotional

expression and behaviour.

The pons (metencephalon) consists of two

parts: the tegmentum, a phylogenetically

older part that contains the reticular

formation, and the pontine nuclei, a larger

part composed of masses of neurons that lie

among large bundles of longitudinal and

transverse nerve fibres. The pons relays

sensory information between the cerebellum

and cerebrum, aids in relaying other

messages in the brain, controls arousal, and

regulates respiration (see respiratory

centres).

The medulla oblongata (myelencephalon),

the most caudal segment of the brainstem,

appears as a conical expansion of the spinal

cord. The roof plate of both the pons and the

medulla is formed by the cerebellum and a

membrane containing a cellular layer called

the choroid plexus, located in the fourth

ventricle. Cerebrospinal fluid entering the

fourth ventricle from the cerebral aqueduct

passes into the cisterna magna, a

subarachnoid space surrounding the

medulla and the cerebellum, via openings in

the lateral recesses in the midline of the

ventricle. The medulla contains nuclei

associated with the hypoglossal, accessory,

vagus, and glossopharyngeal cranial nerves.

In addition, it contains portions of the

vestibular nuclear complex, parts of the

trigeminal nuclear complex involved with

pain and thermal sense, and solitary nuclei

related to the vagus, glossopharyngeal, and

facial nerves that subserve the sense of

taste. Summarily, the medulla oblongata

oblongata controls autonomic functions, and

relays nerve signals between the brain and

spinal cord. It is also responsible for

controlling several major points and

autonomic functions of the body: respiration

(via dorsal respiratory group and ventral

respiratory group), blood pressure, heart

rate, swallowing, vomiting, defecation.

48. Which of the following animals were

used in the first experiments to do

pregnancy tests in humans?

39

1 White rats

2 Pigs

3 Spur-toed frog

4 Field mice

5 Dogs


Biological tests for pregnancy depend upon

the production by the placenta (the

temporary organ that develops in the womb

for the nourishing of the embryo and the

elimination of its wastes) of chorionic

gonadotropin, an ovary-stimulating

hormone. In practice, the tests have an

accuracy of about 95 percent, although

false-negative tests may run as high as 20

percent in a series of cases. False-negative

reports are frequently obtained during late

pregnancy when the secretion of chorionic

gonadotropin normally decreases. The

possibility not only of false-negative but also

of false-positive tests makes the tests, at

best, probable rather than absolute evidence

of the presence or absence of pregnancy.

Chorionic gonadotropin in a woman's blood

or urine indicates only that she is harbouring

living placental tissue. It does not tell

anything about the condition of the foetus. In

fact, the greatest production of chorionic

gonadotropin occurs in certain placental

abnormalities and disorders that can

develop in the absence of a foetus. Tests

using immature mice (the Aschheim-Zondek

test) and immature rats have been found to

be extremely accurate. Tests using rabbits

(the Friedman test) have been largely

replaced by the more rapid and less

expensive frog and toad tests. The use of

the female South African claw-toed tree

toad, Xenopus laevis, is based on the

discovery that this animal will ovulate and

extrude visible eggs within a few hours after

it has received an injection of a few millilitres

of urine from a pregnant woman. The male

common frog, Rana pipiens, will extrude

spermatozoa when treated in the same way.

Both of these tests are considered

somewhat unsatisfactory because false-

positive reactions are not uncommon.

49. Under which conditions will plants

have a low transpiration rate?

1 High temperatures

2 High humidity

3 Strong winds

4 Lots of ground water

available

5 More light


Transpiration is the plant's loss of water,

mainly through the stomates of leaves.

Stomates consist of two guard cells that

form a small pore on the surfaces of leaves.

The guard cells control the opening and

closing of the stomates in response to

various environmental stimuli. Darkness,

internal water deficit, and extremes of

temperature tend to close stomates and

decrease transpiration; illumination, ample

water supply, and optimum temperature

open stomates and increase transpiration.

40

The exact significance of transpiration is

disputed; its roles in providing the energy to

transport water in the plant and in aiding in

heat dissipation in direct sunlight (by cooling

through evaporation of water) have been

challenged. Stomatal openings are

necessary to admit carbon dioxide to the

leaf interior and to allow oxygen to escape

during photosynthesis, hence transpiration

has been considered by some authorities to

be merely an unavoidable phenomenon that

accompanies the real functions of the

stomates.

50. Which disease is not waterborne?

1 Cholera

2 Malaria

3 Scurvy

4 Yellow fever

5 Diarrhoea

Answer 3: (Encyclopaedia Britannica)

Cholera is an intestinal disease that is the

archetype of waterborne illnesses. It

spreads by the faecal–oral route: infection

spreads through a population when faeces

containing the bacterium contaminate water

that is then ingested by individuals.

Transmission of the disease can also occur

with food that has been irrigated, washed, or

cooked with contaminated water. Foods that

have the greatest potential to transmit the

disease include shellfish and seafood,

especially if eaten raw; fruits and vegetables

grown in soil that has been either fertilized

with human excrement (night soil) or

irrigated with raw sewage; and foods packed

in contaminated ice. Vibrio cholerae is a

member of the family Vibrionaceae, which

includes three medically important genera of

water-dwelling bacteria. It is a short, gram-

negative, rod-shaped bacterium that

appears curved when isolated. There are

about 140 types of V. cholerae, based on

the classification of a protein called the O

antigen in the bacterium's cell wall. The only

strains of V. cholerae known to cause

cholera—strains O1 and O139—have the

ability to produce a type of toxin called an

enterotoxin. Not all V. cholerae O1 produce

the toxin.

Scurvy (also called vitamin C deficiency) is

one of the oldest-known nutritional disorders

of humankind, caused by a dietary lack of

vitamin C (ascorbic acid), a nutrient found in

many fresh fruits and vegetables,

particularly the citrus fruits. Vitamin C is

important in the formation of collagen (an

element of normal tissues), and any

deficiency of the vitamin interferes with

normal tissue synthesis, a problem that

underlies the clinical manifestations of the

disorder. Scurvy is characterized by swollen

and bleeding gums with loosened teeth,

soreness and stiffness of the joints and

lower extremities, bleeding under the skin

and in deep tissues, slow wound healing,

and anemia.

Yellow fever is an acute infectious disease,

one of the great epidemic diseases of the

tropical world, though it sometimes has

occurred in temperate zones as well. The

disease, caused by a flavivirus, infects

41

humans, all species of monkeys, and certain

other small mammals. The virus is

transmitted from animals to humans and

among humans by several species of

mosquitoes. Yellow fever appears with a

sudden onset of fever, chills, headache,

backache, nausea, and vomiting. The skin

and eyes may appear yellow—a condition

known as jaundice and a sign that gives rise

to the disease's popular name. There is no

specific treatment for those with yellow fever

beyond good nursing and supportive care.

However, yellow fever is an outstanding

example of a completely preventable

disease. People can be rendered immune to

the virus through vaccination, and outbreaks

can be contained by eliminating or

controlling mosquito populations. Thanks to

such measures, the great yellow fever

epidemics of the late 19th and early 20th

centuries are no more, though the disease is

still present in tropical Africa and South

America, where access to vaccine is

sometimes lacking and the virus is held in

vast natural reservoir by forest monkeys.

Diarrhoea is abnormally swift passage of

waste material through the large intestine,

with consequent discharge of loose faeces

from the anus. Diarrhoea may be

accompanied by cramping. The disorder has

a wide range of causes. It may, for example,

result from bacterial or viral infection; from

dysentery, either amoebic or bacillary; from

impaired absorption of nutrients; from eating

coarse or highly seasoned foods or drinking

large quantities of alcoholic beverages; from

poisons such as arsenic or mercury

bichloride; or from drugs administered to

reduce high blood pressure. Excessive

amounts of thyroid hormones, parathyroid

hormone deficiencies, irritable bowel

syndrome, and uremia (an excess of

nitrogenous wastes in the blood) all may

cause diarrhea. Most cases of diarrhea are

not serious and do not require treatment;

dehydration can be prevented by drinking

plenty of clear liquids. Diarrhea caused by

an infection can often be treated with

antibiotics.

Malaria is an intermittent and remittent fever

caused by a protozoan parasite that invades

the red blood cells. The parasite is

transmitted by mosquitoes in many tropical

and subtropical regions. The parasite

belongs to the genus Plasmodium (phylum

Sporozoa) and is transmitted by female

mosquitoes of the genus Anopheles.

ORIGIN: mid 18th cent.: from Italian, from

mal'aria, contracted form of mala aria ‘bad

air.’ The term originally denoted the

unwholesome atmosphere caused by the

exhalations of marshes, to which the

disease was formerly attributed.

40 th national science olympiad: 4 march 2004 questions … · 2019-01-08 · 1 40 th national...

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